The present invention is in the field of of optical instrumentation. More particularly, the present invention is directed to an improved mounting and drive apparatus for use with astronomical instruments, such as telescopes and cameras, when viewing or optically recording celestial bodies.
There are two basic types of telescope mounts: altazimuth and equatorial. Both types have two orthogonal axes of rotation. In the altazimuth mount, as the name implies, a first axis is horizontal and permits altitude to be adjusted by pivoting thereabout and a second axis is vertical, which permits the azimuth to be selected. In the equatorial mount, a first or polar axis is parallel to the earth's axis (made so by inclining it to the horizontal by an angle equal to the latitude of the viewer) and the second declination axis permits adjustment of the angle of inclination. Tracking of a celestial object is very difficult with the altazimuth mount, requiring complicated (and therefore expensive) drive apparatus to coordinate the complex multiplanar motions. The equatorial mount makes celestial tracking much simpler: the object is located, the declination axis fixed, and the optical instrument rotated about the polar axis in a direction opposite to, and at a rate equal to the rate of, the earth's rotation. This is known as driving the telescope in right ascension (so known for the path followed by the light receiving end of the instrument).
Because of the simplicity of tracking with the equatorial mount, it is used on virtually all professional telescopes and a good many of the amateur instruments, as well. However, due to the comparitive ease of setup, some amateur astronomers still prefer the altazimuth to the equatorial mount. Typically, the equatorial mount is complicated by the need to lock the optical instrument into the mount to prevent possible dropping of the instrument as the mount rotates about the polar axis. These securement or locking means increase setup and takedown for the optical instrument. Further, the worm gears typically used in the equatorial drive systems are relatively expensive making them less accessible to many amateur astronomers. Finally, the rotation of the equatorial mount about the polar axis sometimes produces an inconvenient or even inaccessible location for the eyepiece lens.
The present improved mounting and drive system for optical instruments solves these problems. A safety trunnion turns a mount suitable for use in an equatorial system. A V-shaped trunnion has an entrance channel which has a first component that extends generally vertically and a second component that is angulated downwardly relative to the first forming a crook at the juncture and an angle with the first component preferably between 75.degree. and 135.degree.. In the event the trunnion becomes inverted as a result of a rotation of the mounting bracket about the polar axis, the mounting studs will slip down into the crook and the second (now upwardly extending) component of the entrance channel will retain the optical instrument in the mounting bracket.
The cross section of the optical instrument is configured as a polygon, preferably a hexagon, with a declination mounting stud protruding from each face. Declination studs protruding from opposing faces provide mounting pairs pivotally received in the trunnion. Should any particular pair of declination studs provide an inconvenient viewing angle, the instrument may be readily lifted out of the trunnion and rotated so that the eyepiece occupies a more convenient location and the appropriate pair of declination studs quickly and easily reinserted in the safety trunnion.
Lastly, a guided sector drive having a linear threaded drive rod provides an inexpensive drive mechanism for slewing the optical instrument in right assention to track a celestial object. A pair of curved lateral guides keep the driven surface of the sector in contact with the drive rod. The driven surface may comprise a curved, threaded rod section that is attached to the end of the sector or an impressionable coating material bonded thereto. The impressionable coating material may comprise an epoxy, an adhesive tape, or the like. Other features, advantages, and characteristics of the present invention will become apparent after a reading of the following detailed description.